This invention relates to phototherapy, and more particularly to phototherapy by means of a catheter.
Photodynamic therapy (PDT) is a treatment modality using light of an appropriate wavelength to activate a photosensitizer in the presence of oxygen, resulting in localized tissue necrosis. The depth of light penetration, and consequently of the tissue necrosis, is a function of light wavelength, and is typically less than one centimeter. This depth limitation characteristic makes PDT an ideal treatment for tissues with superficial lesions.
Barrett""s esophagus (BE) is one such lesion which is an ideal target for PDT. It is a lesion of the superficial lining of the esophagus characterized by the replacement of the normal stratified squamous epithelium by a metaplastic columnar epithelium. It is an acquired condition that develops predominantly from chronic gastroesophageal reflux disease (GERD). BE appears endoscopically as finger-like projections or islands of epithelium. Patients with BE are at risk for the development of dysplasia. On a background of dysplastic epithelium, esophageal adenocarcinoma may then develop. Barrett""s esophagus with dysplasia, therefore, has been identified as a premalignant condition. The estimated risk for developing adenocarcinoma in patients with this condition has been reported to be from 30 to 169 times greater than that of the general population.
The management of BE with high grade dysplasia is somewhat controversial. Some advocate close observation with regular endoscopy and biopsies until esophageal cancer is found. Unfortunately, treatment after documentation of frank invasive cancer may result in lower cure rates. Some advocate total esophagectomy before cancer is found. There is, however, a substantial morbidity and mortality associated with this type of radical surgery. Therefore, a minimally invasive technique such as PDT should be ideal for lesions such as those of BE. Several studies have reported on the use of PDT for treatment of BE and also of superficial carcinoma. Extensive mucosal ablation was noted with abolishment of high grade dysplasia or superficial carcinoma in the majority of patients.
Improved photodynamic therapy apparatus and methods are desired.
A remaining problem with treatment of BE by use of photosensitive medications is that the dose of photosensitizer medication at the region of treatment, and the incident light dose (fluence) acting on the region of treatment, are difficult to control.
A phototherapy method according to the invention includes the step of administering a photosensitive medication to a patient, which medication fluoresces in response to light flux. Energy is applied to a proximal end of a catheter adjacent tissue of said patient, to thereby cause light flux from a distal end of said catheter, whereby the light flux causes the photosensitive medication to fluoresce. A signal is generated which is representative of one of (which is to say, is either or both of) the light flux and the fluorescence. The signal so generated, which may be either in the form of a light sample or an electrical signal, is coupled by way of the catheter to a location without (outside of) the patient. The signal may be analyzed to determine any of several parameters.
A phototherapy method according to another aspect of the invention includes the steps of administering a medication to a patient, which medication, when activated by light flux, both leads to tissue necrosis and fluoresces within a specific range of wavelengths in response to light flux. Light flux is applied to a vas (any tube-like anatomical organ, duct, or cavity, including, but not limited to, esophagus, blood vessels, lymphatics, urethra, lung/trachea, cervix, oral cavity, and rectum) of the patient through a catheter (which may be introduced into the vas directly, or by penetration through tissue, such as muscle tissue, as by means of a needle), for thereby performing phototherapy, and causing the medication to fluoresce in response to the flux. At least a portion of the fluorescent light is routed to a location without the patient by means of the catheter. The method includes the further step of establishing, from at least the fluorescence, at least one of (a) the intensity of the applied flux and (b) the duration of the applied flux.
In a particular mode of the method of the invention, the step of determining from at least the fluorescence includes the step of determining at least one of the power and the intensity of the fluorescence. In a particular mode, the step of administering medication includes the step of administering 5-aminolevulinic acid orally. The medication may also be injected or administered topically. According to this particular mode, the step of applying light flux includes the step of applying a light flux having its peak amplitude at a wavelength in the vicinity of 5 (10xe2x88x927) meters. This may be accomplished, in one version, by generating white light, and passing the white light through an optical bandpass filter having a peak in transmission response in the vicinity of 5 (10xe2x88x927) meters.
In a preferred mode of practicing the method of the invention, the step of applying light flux includes the step of applying electrical excitation to a plurality of semiconductor light sources associated with a distal portion of the catheter, which semiconductor light sources produce light in the vicinity of 5 (10xe2x88x927) meters.
The inventive method may also include, before the step of administering medication, the sensing of the fluorescence of the vas of the patient in response to a flux of light.
According to another aspect of the invention, a catheter for phototherapy comprises an elongated body defining an axis of elongation, a distal region, and a proximal region, which distal region is adapted for introduction into a vas of a patient. An elongated array of semiconductor light sources is associated with the catheter body near the distal region. The semiconductor light sources and the body near the semiconductor light sources are such that, when the light source(s) are energized, light from the semiconductor light source(s) can radiate away from the body of the catheter. An electrical energization arrangement extends along the length of the body from the proximal region to the array, for energizing at least some of the semiconductor light sources of the array. The light sources of the array may be coupled in parallel, series, or series-parallel. In order to render the illumination of the walls of the vas more uniform, a dispersive element may be used, such as a frosted coating, which may be provided by sapphire powder, or by use of intralipid solutions of various concentrations. Preferably, the energization arrangement provides for independent energization of various portions of the light array. A balloon may be associated with the distal region of the catheter. Such a balloon has a membrane which is at least translucent to the light produced by the semiconductor light sources, whereby light radiated away from the semiconductor body in the distal region can pass through the membrane of the balloon to impinge on the walls of the vas. The balloon may provide the optical dispersion. This catheter also includes a balloon inflation lumen extending from the proximal region of the catheter to the balloon, so that the balloon may be inflated within the vas. Inflation of the balloon tends to flatten folds in the wall of the vas, and energization of the semiconductor light sources allows light to reach the wall of the vas. In the presence of a fluorescent photosensitive substance in the wall of the vas, the light reaching the wall of the vas results in fluorescence of the photosensitive substance. The catheter further includes a fluorescence light pickup and transmission arrangement located in the distal region, for picking up the fluorescence light, and for carrying a signal responsive to the fluorescence light to the proximal region, and for making the signal responsive to the fluorescence light available at the proximal region of the catheter. This fluorescence light pickup and transmission arrangement may comprise a photosensor such as a photodiode associated with the distal region of the catheter, for receiving the fluorescence light, and for generating an electrical signal in response to the fluorescence light, and some arrangement for conducting the electrical signal to the proximal end of the catheter. As an alternative, the fluorescence light pickup and transmission arrangement comprises an optical fiber extending from the distal region to the proximal region of the catheter. For this purpose, the distal end of the optical fiber is adapted for receiving a portion of the fluorescence light, and for coupling the portion of the fluorescence light into the optical fiber, whereby the portion of the fluorescence light in the optical fiber is the signal responsive to the fluorescence light. In a particular embodiment, the distal end of the optical fiber is made into an approximately spherical shape.